MOSCOW (AFP) - A Russian
scientist has reopened the controversy over a gigantic explosion in 1908
in Siberia with a claim that he has found debris from an extraterrestrial
space vehicle, or UFO, which collided with a comet.

On June 30, 1908 a colossal flash lit up the sky over
Siberia, followed by an explosion with the power of a thousand atom bombs.
It obliterated the taiga (forest) for hundreds of square kilometres (miles)
in the basin of the river Podkamennaya Tunguska in the Krasnoyarsk region.

People living in the villages of Siberia thought there
had been an earthquake. Humans and animals were thrown to the ground by
the shockwave, windows were blown in.

No meteorite debris was found and scientists conclude
that the core of a comet or an asteroid had exploded.

Researcher Yuri Lavbin has spent 12 years researching
the mystery of the "Tunguska meteorite" and believes he has found
the key to one of the great scientific enigmas of the last century, though
many scientists remain sceptical.

He is president of the "Tunguska Spatial Phenomenon"
Foundation in Krasnoyarsk, made up of some 15 enthusiasts, among them geologists,
chemists, physicists and mineralogists, who have been organising regular
expeditions to the area since 1994.

Lavbin's theory is that a comet and a mysterious flying
machine collided 10 kilometres (six miles) above the earth's surface causing
the explosion.

He and his team say that on an expedition to the Podkamannaya
Tunguska river in July they found, between two villages, two strange black
stones in the form of regular cubes with their sides measuring a metre
and half (five feet).

These stones "are manifestly not of natural origin,"
Lavbin says. They appear to have been fired and "their material recalls
an alloy used to make space rockets, while at the beginning of the 20th
century only planes made of plywood existed."

He claims that the cubes are the remains of a flying
machine, perhaps an extraterrestrial spaceship, while admitting that an
analysis of the stones has yet to be undertaken.

He found something else: a huge white stone "the
size of a peasant's hut" stuck in the top of a crag in the middle
of the devastated forest.

"Local people call it the 'reindeer stone'. It is
made of a crystalline matter which is not typical of this region,"
Lavbin said. He suggests it is part of the core of a comet.

The scientific establishment is not convinced.

"There are plenty of amateurs who organise trips
to the site of the Tunguska cataclysm," said Anna Skripnik of the
meteorites committee of the Academy of Sciences.

"In Siberia where oil geologists regularly work
you can find a heap of fragments of various machines."

Lavbin is not deterred. He produces satellite photos
of the region to back his theory which show the "footprints"
of the spaceship (long marshes and lakes) and of the comet (devastated
forests, charred trees and smashed rocks).